Radiofrequency transformer and ribbon winding therefor



Dec. 18, 1934. F C MOLTER 1,984,979

RADIO FREQUENCY TRANSFORMER AND RIBBON WINDING THEREFOR Filed Sept. 25, 1931 gwuentoo fled ,C- Molten Patented Dec. 18, 1934 STATES PATENT OFFICE RADIOFREQUENCY TRAN SFORMIER AND RIBBON WINDING. THEREFOR Fred C. Molter, superior, Wis. I Application September 25, 1931, Serial No. 565,191

1 Claim. (01. -459) I This invention relates generally to high frequency receivingapparatus such as is'used in wireless telegraphy and radio, but more particularly to the construction of the radio transformers utilized in such apparatus.

One object of the invention is to provide a transformer in which the primary coil has the least possible resistance to the flow of high frequency current and at the same time will damp out extraneous impulses in the receiving set usually caused by currents of lower frequency.

Another object is to provide a transformer which is of simple and economical construction and will have the features as stated above.

Heretofore, in'the construction of radio receivers, it has been the custom to wrap the primary coils of the radio frequency transformer with ordinary conducting wire, generally of copper and insulated by being either cotton or silk covered or enameled. In such transformers many losses occur in the reception of the signals. These losses not only affect the quality of the sounds emanating from the speaker but also require that the set be provided with more powerful amplifying units in order that the sounds will be plainly audible.

With the construction which constitutes the subject matter of this invention these deleterious effects are eliminated, since the primary coil of the radio frequency transformers are constructed with suflicient surface and of such shape to freely receive and transmit the incoming radio frequency waves, thus both adding to the efliciency and tone of the apparatus.

Briefly stated my improved apparatus consists primarily in an improved radio frequency transformer of the open or air core type having a primary coil of flat or ribbon shaped conducting material, and a secondary or grid coil wound of the ordinary wire, having a circular cross section.

Referring to the drawing, in which similar parts are represented by like numerals:

Figure 1 shows one type of transformer wherein the primary and secondary coils are wound on concentric cylinders.

Figure 2 shows a type in which both coils are wound on the same cylinder and spaced from each other.

Figure 3 is a diagrammatic view showing the preferred hook-up wherein a transformer having a ribbon type primary is used in a receiver stage.

Figure 4 is a side elevation of a portion of the ribbon type primary coil, and

Figure 5 is a sectional view of the ribbon type coil.

In'Fig'ure 1, the numeral 1' illustrates a cylindrical tube of any suitable insulating material on which is wound a primary coil 2. The coil 2 consists of a suitable length of flat or ribbon shaped conducting material, as shown in Figures 4 and 5, terminating at its ends in a conductive connection with the binding posts 3 and. 4 as shown in Figure 1. When the transformer is used in a receiving stage, as illustrated diagrammatically in Figure 3, the terminals 3 and 4 are preferably connected to the terminals of a potentiometer 5, the central or sliding member 6 of which is connected by the lead in wire 7 to the aerial 8. The terminal 4 of the primary coil 2 is also connected to a ground lead 9.

Within the cylinder 1, on which the ribbon shaped primary coil 2 is wrapped, is an inner concentric cylinder 10 on which the secondary coil 11 is wrapped. The secondary coil is of ordinary insulated wire of circular cross section terminating at its ends 12 and 13 in conductive connections with the binding posts 22 and 23 as shown in Figures 1, 2 and 3. These terminals 12 and 13 are connected respectively to the grid terminal 14 of the first radio tube or to the grid terminal of the detector tube and the other terminal is connected to the negative side of the filament circuit as in the usual hook-up.

A deviation from this form of construction is shown in Figure 2, in which the primary coil 2' is wound on the same tube or cylinder 1' as the secondary and as in the former case one end 3 of the primary is connected to the aerial 8 and the other to the ground. One end terminal 12' of the secondary is connected to the grid terminal 14 of the first radio or detector tube, and the other 13' to the minus filament circuit as shown in the former case.

In either of these cases the secondary is usually bridged by a variable condenser 15 and in the case of the transformer being connected to a detector tube, a fixed condenser 16 and grid leak 17 is interposed between the secondary and the grid. With this type of construction, however, it is especially important that the potentiometer 5 be bridged across the terminals of the primary coil in order to control the flow of current therein, and a fixed condenser 18 is bridged across from the ground terminal 4 of the primary to the grid terminal 12 of the secondary.

It will be seen from this type of construction that there is not only an inductive, but also a condenser action between the primary and secondary, thus permitting the ready flow of high frequency currents, but acting as a choke to low frequency currents, thus permitting the passage of the entire radio impulses but blocking extraneous vibrations with their consequent noises from the receiver.

Thus my improved transformer not only provides a better path for the passage to radio waves, but also provides a filter which prevents unwanted impulses from affecting the grid and thus eliminates them from the speaker.

The novel features and the operation of this device will be apparent from ,the foregoing description. While the device has been shown and the structure described in detail, it is obvious that this is not to be considered limited to the exact form disclosed and that changes may be made therein within the scope of what is. claimed without departing from the spirit of the invention.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

width, and a secondary coil consisting of a circular shaped conductor helically wound upon the outside of the inner clyinder with the adjacent convolutions thereof spaced apart a distance less than the diameter of said circular conductor (whereby the distributed capacity between said adjacent turns of the primary is small as compared with the distributed capacity between ad- .J'acent turns of the secondary).

FRED C. MOLTER. 

